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lzjb_original.c
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lzjb_original.c
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#include <stdint.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/param.h>
#define NBBY 8 // число бит в байте
#define MATCH_BITS 6
#define MATCH_MIN 3
#define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1))
#define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
#define LEMPEL_SIZE 1024
/*ARGSUSED*/
size_t
lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
{
uint8_t *src = s_start;
uint8_t *dst = d_start;
uint8_t *cpy;
uint8_t *copymap = NULL;
int copymask = 1 << (NBBY - 1);
int mlen, offset, hash;
uint16_t *hp;
uint16_t lempel[LEMPEL_SIZE] = { 0 };
while (src < (uint8_t *)s_start + s_len) {
if ((copymask <<= 1) == (1 << NBBY)) {
if (dst >= (uint8_t *)d_start + d_len - 1 - 2 * NBBY)
return (s_len);
copymask = 1;
copymap = dst;
*dst++ = 0;
}
if (src > (uint8_t *)s_start + s_len - MATCH_MAX) {
*dst++ = *src++;
continue;
}
hash = (src[0] << 16) + (src[1] << 8) + src[2];
hash += hash >> 9;
hash += hash >> 5;
hp = &lempel[hash & (LEMPEL_SIZE - 1)];
offset = (intptr_t)(src - *hp) & OFFSET_MASK;
*hp = (uint16_t)(uintptr_t)src;
cpy = src - offset;
if (cpy >= (uint8_t *)s_start && cpy != src &&
src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) {
*copymap |= copymask;
//printf("copymap = %02X\n", *copymap);
for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++)
if (src[mlen] != cpy[mlen])
break;
*dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) |
(offset >> NBBY);
*dst++ = (uint8_t)offset;
src += mlen;
} else {
*dst++ = *src++;
}
}
return (dst - (uint8_t *)d_start);
}
/*ARGSUSED*/
int
lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
{
uint8_t *src = s_start;
uint8_t *dst = d_start;
uint8_t *d_end = (uint8_t *)d_start + d_len;
uint8_t *cpy;
uint8_t copymap = 0;
int copymask = 1 << (NBBY - 1);
while (dst < d_end) {
if ((copymask <<= 1) == (1 << NBBY)) {
copymask = 1;
copymap = *src++;
}
if (copymap & copymask) {
int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;
int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;
src += 2;
if ((cpy = dst - offset) < (uint8_t *)d_start)
return (-1);
while (--mlen >= 0 && dst < d_end)
*dst++ = *cpy++;
} else {
*dst++ = *src++;
}
}
return (0);
}